This invention relates to a trench shield used for the protection of workers operating in excavations. In particular, the present invention is directed to the provision of a lightweight trench shield capable of providing the necessary protection to a trench worker while being capable of movement by a single worker along an excavation without the use of mechanical equipment.
A trench shield is a protective structure that is intended to protect workers as they conduct operations below the ground surface, for example laying pipe and running footings for structures. The trench is typically of significant length to require the movement of the shield therealong as the work site advances. In the case of trench shields utilizing steel face plates with spreaders therebetween, the weight of the shield has required the use of equipment, such as a backhoe, to advance the shield along the trench. The need for equipment coupled with the additional manpower has generated interest in the development of trench shields that possess a high strength to weight ratio and satisfy the governmental regulations specifying loading capability.
Trench shields utilizing different materials for the adjacently spaced side panels have been proposed. Examples include the use of corrugated metal panels, molded composite lightweight panels and lightweight wood blocks oriented to utilize the directional strength properties of wood. These proposed shields have not found acceptance either due to cost of manufacture, lack of durability and inability to withstand prescribed loading requirements.
Accordingly, the present invention is directed to a lightweight trench shield that has a strength to weight ratio that enables a worker to advance the shield along the trench without assistance. Further, the subject trench shield utilizes spreader supports which distribute the loading on the spaced panels outwardly thereby enhancing load bearing capability. The side panels are constructed with regions proximate to the spreader supports capable of withstanding greater loading than other regions of the panel. Thus, the present trench shield is capable of providing protection while possessing the capability of being moved by a single worker along the trench.